Diomedes
et al | method = | site = | pronounce = Dīyōmēdēs | adjective = Diomedian | dino = Taemotoj | planet_numbers = P179, HD 164922 P1, Hercules P6, Tarandus P29, 2006 P18, 2006 Her-3, 2006 Tar-5 | star_designations = PS 144 b, P5 Herculis b, P25 Tarandi b, 164922 b, 88348 b, 700.2 b, GJ 9613 b, 85678 b | star = HD 164922 | constellation = | lactoph = Tarandus | ra = 270.6286111° | dec = +26.3130000° | distance = 22.120 72.145 0.62083 4.5623 | planets = Tydeus (hypothetical) Deipyle (hypothetical) | semimajor = 2.109336 315.5522 196.0774 Mmi 10.226352 μpc 17.54282 503.36 stellar radii | semiminor = 2.106441 AU 315.1191 Gm 195.8083 Mmi 10.212315 μpc 17.51874 lmin 502.67 stellar radii | periastron = 1.998854 AU 299.0243 Gm 185.8073 Mmi 9.690718 μpc 16.62396 lmin 476.99 stellar radii | apastron = 2.219819 AU 332.0802 Gm 206.3475 Mmi 10.761986 μpc 18.46167 lmin 529.72 stellar radii | eccentricity = 0.0523778 | orbital_circ = 13.24671 AU 1981.679 Gm 1231.373 Mmi 64.22185 μpc 110.1695 lmin | orbital_area = 13.95870 AU2 312389.102 Gm2 120616.97 Mmi2 328.09135 μpc2 965.4993 lmin2 | orbital_period = 1154.734584 3.16149099 99.7690681 1978.72 Diomedian rotations | avg_speed = 19.930 12.384 4.19 AU/yr 0.6459 ppc/s 66.5 lμs/s | max_speed = 20.445 km/s 12.704 mi/s 4.30 AU/yr 0.6626 ppc/s 68.2 lμs/s | min_speed = 19.401 km/s 12.055 mi/s 4.08 AU/yr 0.6287 ppc/s 64.7 lμs/s | orbit_direction = | inclination = 76.288° 0.85° to star’s equator 0.57° to | arg_peri = 194.996° | node = 85.699° | long_peri = 280.694 | separation = 95.360 | moons = 86 | rings = 983 | mean_star_size = 0.229° (13.7') | max_star_size = 0.241° (14.5') | min_star_size = 0.217° (13.0') | mean_star_magnitude = –24.663 | max_star_magnitude = –24.780 | min_star_magnitude = –24.553 | mean_radius = 0.7702 8.3662 53.301 33.120 kmi 1.6447 npc 10.668 lj | equatoral_radius = 0.8026 RJ 8.7180 R⊕ 55.542 Mm 34.512 kmi 1.7139 npc 11.116 lj | polar_radius = 0.7378 RJ 8.0144 R⊕ 51.060 Mm 31.727 kmi 1.5755 npc 10.219 lj | mean_circ = 334.900 Mm 208.097 kmi 10.3339 npc 67.026 lj | equatoral_circ = 348.983 Mm 216.848 kmi 10.7685 npc 69.845 lj | polar_circ = 320.817 Mm 199.347 kmi 9.8994 npc 64.208 lj | surface_area = 0.6176 SJ 72.872 S⊕ 37170 Mm2 14350 kmi2 35.39 npc2 1489 lj2 | volume = 0.4752 VJ 609.12 V⊕ 659800 Mm3 158300 kmi3 19.39 npc3 132100 lj3 | oblateness = 0.08410 | aspect_ratio = 0.91929 | mass = 0.3709 117.8901 0.7042 Wg 0.7763 Xt | recip_mass = 2652 | classification = Sub-Jupiter | density = 1.035 g/cm3 | gravity = 1.519 14.89 m/s2 48.85 ft/s2 0.4595 fpc/s2 52.88 lns/s2 | gm = 46.993 × 106 km3/s2 | escape_v = 41.31 km/s 25.67 mi/s 1.339 ppc/s 137.8 lμs/s | hill_radius = 40.53 15.58 Gm 9.68 Mmi 480.7 npc 51.96 292.3 planetary radii | axial_tilt = 3.77° | np_ra = 0.00856° | np_dec = +58.95611° | rot_period = 14.00583 0.583576 50.4210 | rot_velocity = 6.861 km/s 4.263 mi/s 24700 kph 15350 mph 222.4 fpc/s 22.89 lns/s | rot_direction = | cloudtop_temp = 156 (–118 , –180 , 280 ) | c_peri_temp = 160 K (–113°C, –172°F, 288°R) | c_apo_temp = 152 K (–122°C, –187°F, 273°R) | 1bar_temp = 182 K (–91°C, –131°F, 328°R) | irradiance = 188 (0.138 ) | peri_irradiance = 210 W/m2 (0.153 I⊕) | apo_irradiance = 170 W/m2 (0.124 I⊕) | albedo = 0.477 ( ) 0.575 ( ) | peri_albedo = 0.483 ( ) 0.581 ( ) | apo_albedo = 0.469 ( ) 0.572 ( ) | property = Water cloud jovian | scale_height = 41.2 (25.6 , 1.34 ppc, 137.4 ) | 1bar_density = 0.15 g/m3 | molar_mass = 2.10 g/mol | composition = 91.204% (H2) 6.543% (He) 0.921% (H2O) 0.687% (NH4) 0.605% (CH4) 324 ppm (Ne) 2 ppm (HD) 1 ppb (C3H8) Aerosols: (H2O) | dipole_strength = 36 (0.36 ) | magnetic_moment = 7.10 × 1018 T•m3 | dipole_tilt = 8.40° | long_tilt = 28.64° | magnetic_offset = 0.65 Rp (0.091 LU, 0.035 Gm, 1.08 npc, 0.116 ls) | magnetopause = 18.1 Rp (2.51 LU, 0.97 Gm, 29.8 npc, 3.22 ls) | bow_shock = 25.3 Rp (3.50 LU, 1.35 Gm, 41.6 npc, 4.49 ls) | tail_length = 869.8 Rp (120.60 LU, 46.36 Gm, 1430.6 npc, 154.65 ls) | ions = H2O+, H+, O+, NH4+ | loading_rate = 83 kg/s | plasma_density = 102 cm–3 | particle_energy = 64 }} Diomedes (often referred as HD 164922 b) is an which orbits the HD 164922, 72 s or 22 s away in the , which is located in the lactoph Tarandus. Diomedes has a planet number 179. Diomedes was detected on July 15, 2006 by who used the to study the wobble of the star caused by the planet’s gravity. On that same day, four other planets were also announced. Diomedes is similar to Saturn in terms of mass, size, interior structure, and orbital eccentricity, but it orbits much closer to its sun, only 22% the distance between Saturn and the Sun, but still it orbits over twice the distance of Earth to the Sun. But like Saturn, this planet has a and dozens of . The mass classification of this planet is a sub-Jupiter with masses ranging from 0.1 to 0.5 Jupiter masses, and the appearance classification is water cloud jovian with temperatures ranging from 150 K to 300 K (–123°C to 27°C, –189°F to 80°F). Combining with the temperature of this planet, it is classified as mild sub-Jupiter from the planetary temperature classification scheme, with mild donating temperatures ranging from 150 K to 400 K (–123°C to 127°C, –189°F to 261°F). Name and chronology is named after a hero in who got involved in the . Diomedes is the 171st extrasolar planet discovered, not counting on planetary candidates that are speculated to be s. However it is the 179th planet in the list, because the numbers 1-8 belongs to the planets in our solar system in order of the distances from the Sun. It is also the 6th planet discovered in Hercules, 29th in Tarandus, 18th in 2006, 3rd in Hercules in 2006, and 5th in Tarandus in 2006. Orbit and rotation Diomedes orbits the star HD 164922 at a semimajor axis of 2.109 AU or 315.6 Gm and a semiminor axis of 2.106 AU or 315.1 Gm. The orbital distance of this planet ranges from 1.999 AU or 299.0 Gm to 2.220 AU or 332.1 Gm. This corresponds to an orbital eccentricity of 0.0524, which is considerably more circular than most of the detected planets with semimajor axes over 2 AU or 300 Gm. Like the planets in our solar system, Diomedes orbit in the same direction as the rotation of the star. This planet takes 1155 days, 3.16 years, or 99.8 megaseconds to revolve around HD 164922 with an average speed of nearly 20 km/s or over 12 mi/s. The inclination of the orbit, which is important for determining its true mass, is unknown. However its inclination is speculated to be 76.3° to the plane of the Earth’s ecliptic, which is almost edge-on to the observers. The of this planet is only 2.9% greater than the determined by radial velocity method. This planet tilts 3.77° to the plane of its orbit, meaning that Diomedes does not have a considerable seasonal cycle like we have on Earth. This planet takes 14 hours to rotate once on its axis, which is longer than Jupiter and Saturn (10 hours) but not as long as Uranus and Neptune (16-17 hours). Observing the parent star As viewed from the surface of Diomedes at the distance of 2.11 AU, the apparent magnitude of the star HD 164922 is –24.66, which is seven times fainter than the Sun as seen from Earth, due to its greater distance from its star and being less luminous. The angular diameter of a star as viewed from Diomedes is about 45% the angular diameter of the full moon and sun as seen from Earth. Physical characteristics Diomedes is 24% more massive than , but its radius is 7% smaller than Saturn, making the planet 48% denser than Saturn and 3.5% denser than water. The planet’s gravity is 1.519 g and falls at 14.89 m/s2. If you weigh 150 lbs on Earth, then you’ll weigh 228 lbs on Diomedes. However, this planet doesn’t have solid surface, like Jupiter and Saturn in our . Atmosphere This planet has a cloudtop temperature of –118°C or –180°F and it is just warm enough to have water clouds with small decks of ammonia clouds. Because the planet orbits in a circular path, it does not change its temperature much throughout its orbit. The difference in temperature between periastron and apastron is only about 9 C° or 15 F°. The change in temperature would be too little to affect the chemical makeup of clouds significantly. On average, the rays from the star reflects about 48% of its radiation striking the planet back into space. Like all planets, the atmosphere of Diomedes composes mainly of and . It also has some amounts of , , and , as well as trace amounts of water ice crystals, , , and . Those trace gases are unique that those gases are not found on giant planets in our solar system. Hydrogen cyanide forms when ammonia reacts with methane gas with the aid of stellar radiation. Some of this gas converts back into ammonia and methane. There is propane in the atmosphere instead of , which is found on all four giant planets in our solar system. Weather The weather on Diomedes would be similar to Saturn, but winds on this planet would be faster than Saturn since the planet orbits lot closer to HD 164922 than Saturn is to the Sun. There could be "Great White Spot" on Diomedes, like Saturn has a . At the poles, there could even be hexagonal hurricane-like storm like it is found on Saturn that was discovered by spacecraft. However unlike Saturn, all storms on Diomedes are powered by the star as the planet receives 40 times more heat from the star than Diomedes radiating heat from the interior. Interior It is speculated that its interior is similar to Saturn because of its similar mass and size to Saturn. As we get deeper into the planet, the temperature and pressure increases. Underneath its thick outer envelope, Diomedes has mantles of liquid hydrogen and helium, despite the temperature is really hot. On Earth, liquid hydrogen can only be produced when we cool the hydrogen gas to below 20 K (–253°C or –423°F) and liquid helium can only be produced when we cool the helium gas to below 4 K (–269°C or –452°F). But inside Diomedes, the reason why there is liquid hydrogen and helium because the pressure is so great that it forces hydrogen molecules and helium atoms closer together despite its increasing temperature. Deeper below, liquid hydrogen can conduct electricity, known as . Below that layer lies a rocky core with a mass of 29 Earth masses (roughly 25% the total mass of its planet) and composes primarly of iron and silicates. The temperature of its core is about 12,100°C or 21,900°F. Magnetosphere Like most planets in our solar system, Diomedes has . The strength of magnetic field is about 17% stronger than Earth’s, over 70% stronger than Saturn’s, and one-twelves of Jupiter’s. The mass loading rate is 83 kg/s, which is similar to the average mass of humans. This magnetic field is produced by the movements of metallic hydrogen in its interior caused by the planet’s rotation. This mechanism is well known as . The magnetic field blocks most of stellar and from reaching the planet, but occasionally it can produce s when the stellar radiation got caught in the magnetic field lines and move towards their where it interact with the planet’s upper atmosphere. Moons and rings Diomedes has 86 moons with at least 1 km across, but objects smaller than 1 km that orbits the planet are called s. The largest moon has about the size of , the largest moon of Saturn. This moon has lakes of ammonia, analogous to lakes of methane on Titan. Other moons are cratered, barren, or covered in ice with subsurface oceans. Diomedes has a ring system about 83% as wide as Saturn, but dark. The ring particles are grains of dust and bits of rocks and boulders but little ice. This ring system formed when an asteroid impacted the tiny moon close to its planet and flung too close that tidal forces of the planet broke the moon apart into bits of rocks and boulders along with grains of dust. The ring system has divisions similar to Saturn’s . Future studies Even though Diomedes has an inclination of 76.3°, this planet is not edge-on enough to transit its star. If Diomedes actually its star, then its inclination, radius, and other parameters can be determined as well as studying its atmosphere and looking for moons and rings. If Diomedes does not transit its star, then Diomedes can be studied by . However with the current technology, it is not capable to find transits of planets with periods over a year. Currently, the transiting planet with the longest orbital period is 111.4 days (0.305 year), which is the planet Niobe ( ). Finding planets with direct imaging orbiting as close as 2 AU from the star is difficult because the glare of its star prevents astronomers from seeing close-orbiting planets. But in 2010, there is a new direct imaging instrument, called (VVC), that can detect and characterize planets as close to their stars as 1 AU. Category:Articles Category:Extrasolar planets Category:Sub-Jupiters Category:Water cloud jovians